Evergladessubtropical saw-grass marsh region, a “river of grass” up to 50 miles (80 km) wide but generally less than 1 foot (0.3 metre) deep, covering more than 4,300 square miles (11,100 square km) of southern Florida, U.S. Through it, water moves slowly southward to mangrove swamps bordering the Gulf of Mexico to the southwest and Florida Bay to the south. To the east the marsh reaches near the narrow, sandy belt that includes the Miami metropolitan area, and to the west it merges into Big Cypress Swamp. The name Everglades is a term unique to Florida. Glade has been used to refer to an open, grassy area in the forest or a moist, swampy area; ever may have referred to the marsh’s seemingly interminable expanse.

Natural environment

The Everglades occupies a shallow limestone-floored basin that slopes imperceptibly southward at about 2.4 inches per mile (about 4 cm per km). Much of it is covered with saw grass (a sedge, the edges of which are covered with minute sharp teeth), which grows to a height of 4 to 10 feet (1.2 to 3 metres). Open water is sometimes found. Slight changes in the elevation of the land and the water’s salt content create different habitats. The Florida Bay estuary is covered with sea grass and serves as a nursery for fish. Mangroves also serve as nurseries and as feeding grounds for wading birds in tidal areas where fresh and salt water combine. Coastal prairie regions support salt-tolerant succulents and cordgrass. Hardwood hammocks consist of thick stands of tropical (mahogany, cocoplum, and strangler fig) and temperate (saw palmetto, live oak, and red maple) trees growing on slight hills, creating islands in the saw-grass marsh and sloughs; domes of cypress or willow can also be found. Pinelands, dominated by slash pine, occupy dry ridges.

The organic soils, formed from the decay of lush vegetation, range from discontinuous shallow patches to accumulations of peat and muck 8 to 10 feet (2.4 to 3 metres) thick near Lake Okeechobee. The best soils are deep mucks found in a narrow zone along the lakeshore, where a dense tangle of custard apple, or pond apple, once grew.

The climate of the Everglades is tropical to subtropical and is influenced strongly by the southeast trade winds. Monthly mean temperatures range from 63 °F (17 °C) to 82 °F (28 °C), though winter frosts occur on rare occasions. Rainfall averages 40 to 65 inches (1,000 to 1,650 mm) annually, with most coming between May and October. During that period the land is nearly covered with a sheet of water. In the dry season (December–April), however, water levels drop and leave it dotted with small pools.

The marsh provides habitat for more than 350 bird species. There are wading birds such as egrets, herons, roseate spoonbills, and ibis; shore and water birds such as terns, plovers, rails, and sandpipers; birds of prey including owls, hawks, and osprey; and a wide variety of songbirds. Several game fish species make their homes there. The Everglades is known for its population of alligators; bobcats, white-tailed deer, river otters, gray foxes, and many types of snakes, lizards, and turtles also live there. The area provides habitat for endangered species such as the manatee, Florida panther, wood stork, American crocodile, and several species of sea turtle. The population of wading birds in the Everglades has fallen drastically since the mid-20th century.

Early inhabitants

To the Native Americans of the region, the Everglades was known as Pa-Hay-Okee (“Grassy Water”). Its vast areas of open saw grass were used as passage for dugout canoes and as hunting and fishing territory. Although there was little settlement within the Everglades, mounds remain to indicate occupancy. The nearby coastal regions were inhabited by Calusa and Tequesta Indians when European explorers first arrived in the 16th century. Contact with Europeans was marked by warfare, disease, and other depredations, and both these groups were largely gone from the region by the late 1700s. Creek peoples then began to move into the area and became known as Seminoles.

The Seminoles found sanctuary in the swamps and marshes because the white settlers did not covet the glades at the time. They developed the “chickee,” a dwelling without walls, made of a log framework with a thatched roof over a raised platform, that assured maximum ventilation. They planted corn (maize), beans, melons, and squash on patches of higher ground and gathered nuts, roots, and palmetto berries. The bulbous roots of the coontie plant were the source of a starchy flour, and hunting and fishing provided much of their sustenance. Most were forced out during the Second Seminole War (1835–42). The Miccosukee tribe (formerly part of the Seminole tribe) continued to make their home in the Everglades into the 21st century.

Development of the Everglades

After the Seminole Wars, which occurred sporadically from 1817 to 1858, interest in the Everglades centred on exploiting its wildlife, especially the heron and egret for their feathers and the alligator for its hide. Drastic reductions in wildlife numbers led to legislation in the early 20th century that protected “plume birds”; alligator hunting was similarly restricted in the 1960s, and the alligator spent several years on the endangered-species list as populations recovered.

Drainage remained the principal focus of engineering in the glades for many years. These projects have been at best a mixed blessing. The natural Everglades drainage system, supplied with fresh water solely by rainfall, once covered more than 11,000 square miles (28,500 square km) from the Kissimmee River basin to Lake Okeechobee and southward to the Gulf of Mexico, Florida Bay, and the Atlantic Ocean. Ranging in depth from 3 feet (0.9 metre) to 6 inches (15 cm), the water slowly flowed southward down the peninsula at a rate of about 100 feet (30 metres) a day. Efforts to drain the marsh began in the 1800s, canal construction in the 1880s, and dredging for agricultural purposes between 1905 and 1910. Laws passed in 1948 required that levees and canals be constructed to prevent flooding in the South Florida region and to provide water for human use. Rainwater was pumped out of the area and released into the ocean or diverted to farms and cities. Everglades water levels were artificially altered in an erratic manner, disturbing the quality, amount, distribution, and timing of the seasonal cycle. In addition, nearly 1,200 square miles (3,100 square km) of land immediately south of Lake Okeechobee was drained and converted to cropland for the production of sugarcane, vegetables, and beef cattle, cutting off the rest of the Everglades from the lake. These changes in the natural water flow as well as runoff from farmland brought about radical alterations in the natural habitat, producing toxic algae, killing sea-grass beds, creating high levels of organic mercury, and flooding seasonal wildlife feeding and nesting sites. Encroaching urban areas and the introduction of exotic species also contributed to ecological problems; roughly half of the original natural Everglades area has now been destroyed.

Efforts to preserve the Everglades ecosystem date to the mid-20th century, notably in the work of conservationists Marjory Stoneman Douglas and Ernest F. Coe. Government discussions on how to reverse the region’s ecological damage began in the early 1970s, initially at the state level but especially after 1990 through federal initiatives. A restoration plan, passed by the U.S. Congress in 2000, was expected to be implemented over several decades. It called for the removal of levees and for changes in water management to more closely mimic the natural process; water pumped out was to be stored in a reservoir system and redistributed onto the land. The plan was intended not only to restore the Everglades environment but to preserve the profitable tourism industry and ensure adequate freshwater supplies for agriculture and the burgeoning population of South Florida. The first phase of the plan got under way in late 2009, when work was started along the Tamiami Trail (a highway along the northern boundary of the national park between Tampa and Miami) to convert a small portion of the roadbed embankment (which acts as a levee) near Miami to a bridge intended to facilitate the southward flow of water at that point.

Everglades National Park encompasses the southwestern portion of the region and is the largest subtropical wilderness left in the United States. The park was authorized in 1934, but, because of difficulties acquiring land, it was not established until 1947. UNESCO designated it (along with Dry Tortugas National Park) a Biosphere Reserve in 1976 and a World Heritage site in 1979. The park has been expanded several times, most recently in 1989. It encompasses 2,357 square miles (6,105 square km), including most of Florida Bay, and preserves a unique blend of temperate and tropical species and freshwater and marine habitats. Part of its northern border adjoins Big Cypress National Preserve. Biscayne National Park is to the east, off the Atlantic coast, and Dry Tortugas National Park lies to the southwest, at the western end of the Florida Keys. Everglades National Park’s several visitor centres have natural history exhibits. The Everglades is popular with boating and canoeing enthusiasts; there are several marked canoe trails, including the 99-mile (159-km) Wilderness Waterway along the park’s western side. Forested areas and the main visitor centre suffered damage from Hurricane Andrew in 1992. The park was placed on the List of World Heritage in Danger in from 1993 to 2007.